1. Field of the Invention
The present invention relates to a scroll compressor for use in, for example, an air conditioner, a refrigerator or the like.
2. Description of Related Art
In view of numerous features including that they are compact and light-weight have, a high operating efficiency and low noise generation and so on, scroll compressors have gained wide market acceptance. Scroll compressors and their operating principles are disclosed in numerous patent and technical literature and are, therefore, well known to those skilled in the art.
As typical examples of the scroll compressor, Japanese Patent Publication (examined) No. 57-49721, published in 1982, discloses a scroll-type fluid machine, while U.S. Pat. No. 4,824,346 discloses a scroll compressor including an eccentric bush mechanism.
FIGS. 5 and 6 depict a conventional scroll compressor and reference thereto will now be made for discussion of the prior art. The conventional scroll compressor shown therein comprises a compressor housing 101 having a rear end portion to which a stationary scroll member 102 in the form of a stationary end plate 103 having a stationary scroll wrap 104 formed on one surface thereof is secured. An orbiting scroll member 106 in the form of an orbiting end plate 107 having an orbiting scroll wrap 108 formed on one surface thereof is accommodated within the compressor housing 101 with the orbiting scroll wrap 108 being in engagement with the stationary scroll wrap 104 of the stationary scroll member 102 to define a plurality of volume-variable sealed working pockets 105 therebetween. The opposite surface of the stationary end plate 103 remote from the stationary scroll wrap 104 is formed with a generally cylindrical partition wall 130 having an end surface secured to the compressor housing 101.
As clearly shown in FIG. 6, the partition wall 130 has a plurality of mounting legs 131 integrally formed therewith and having a thickness greater than that of the partition wall 130. A plurality of bolts 125 extending through a rear wall of the compressor housing 101 are threaded into associated mounting legs 131 to fasten the stationary scroll member 102 to the compressor housing 101.
Referring further to FIG. 5, the opposite surface of the orbiting end plate 107 remote from the orbiting scroll wrap 108 is formed with a generally cylindrical boss 109 in which an annular orbiting bearing 110 is disposed. An eccentric bush 111 in the form of a stud shaft or a disc having a substantial wall thickness and having an eccentric hole 112 defined therein is engaged with and rotatably housed within the annular orbiting bearing 110.
A main shaft 114 has one end formed with an eccentric rod 115 so as to protrude axially from an end surface thereof. The eccentric rod 115 integral with the main shaft 114 is rotatably received in the eccentric hole 112 of the eccentric bush 111 so that, during rotation of the main shaft 114 about its own longitudinal axis, the eccentric rod 115 undergoes an eccentric motion relative to the main shaft 114 to impart an orbiting motion to the orbiting scroll member 106. By this construction, a gaseous medium is introduced into the sealed working pockets 105 which in turn move inwardly around the stationary and orbiting scroll wraps 104 and 108 towards a center discharge port 123 accompanied by progressive reduction in volume thereof. Therefore, the gaseous medium trapped in each sealed working pocket 105 experiences a decrease in volume and an increase in pressure as it approaches the center discharge port 123. Because the center discharge port 123 is opened or closed by a check valve 121, if the pressure inside the working pocket 105 positioned in the proximity of the center discharge port 123 is greater than that of a high-pressure chamber 120 separated therefrom by the check valve 121, the check valve 121 is opened to thereby discharge the compressed gaseous medium accommodated in the working pocket 105 to the high-pressure chamber 120 through the center discharge port 123.
However, the conventional scroll compressor of the above-described construction encounters a problem associated with back-flow of the high-pressure gaseous medium which has been hitherto caused by delayed closure of the check valve 121. In particular, in a scroll compressor having a relatively low compression ratio, the amount of the compressed gaseous medium that flows back into the working pocket 105 from the high-pressure chamber 120 increases, and a resultant reexpansion of the gaseous medium lowers the compression efficiency, thus resulting in a reduction in performance of the scroll compressor.
This conventional scroll compressor has an additional problem in securement of the stationary scroll member 102 within the compressor housing 101. Specifically, forces required to tighten fastening members such as, for example, bolts 125 inevitably generate strains in the stationary scroll member 102 and, hence, no uniform gap can be obtained between the stationary and orbiting scroll wraps 104 and 108, which would eventually result in leakage of the refrigerant. This in turn brings about a reduction in performance of the scroll compressor.